Middlesbrough have made a bid of over £5 million for Paddy McNair.
The Black Cats have already turned down bids for the midfielder from Premier League side Brighton and an unnamed London club for £3.75M.
McNair made 18 appearances and scored five goals last season as Sunderland were relegated from the Championship.
He broke into Manchester United’s first team in 2014 before joining Sunderland in August 2016.
Tony Pulis led Middlesbrough to the Championship play-offs last season but they lost 1-0 on aggregate to Aston Villa in the semi-finals and is hoping to bring McNair to Teeside to go one step better in the coming season.